Answer this question truthfully
### Question: What causes Angioedema?
### Response: Angioedema may be caused by an allergic reaction. During the reaction, histamine and other chemicals are released into the bloodstream. The body releases histamine when the immune system detects a foreign substance called an allergen.
In many cases, the cause of angioedema is never found. The following may cause angioedema:
Animal dander (scales of shed skin). Exposure to water, sunlight, cold or heat. Foods (such as berries, shellfish, fish, nuts, eggs, milk, and others). Insect bites. Medications (drug allergy), such as antibiotics (penicillin and sulfa drugs), nonsteroidal anti-inflammatory drugs (NSAIDs), and blood pressure medicines (ACE inhibitors). Pollen.
Hives and angioedema may also occur after infections or with other illnesses (including autoimmune disorders such as lupus, and leukemia and lymphoma). A form of angioedema runs in families and has different triggers, complications, and treatments. This is called hereditary angioedema, and it is not discussed in this article.